I believe the answer is A, temperature and number of particles are constant. Correct me if i'm wrong :)
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Giddy UP!!!!!!!!!!!!!!!!!!!!!
Relative density, or specific gravity, is the ratio of the density of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water at its densest; for gases, the reference is air at room temperature.
Answer:
6 atm.
Explanation:
Let the mass of both be m
Then moles of He = m/ 4
Moles of Ne = m/ 20
mole fraction of He = Moles of He/ Total moles = m/4/ (m/4 + m/20) = 0.25 m/0.3m = 0.83
Pressure of He = Mole fraction×total pressure = 0.83 × 6 atm = 5 atm
We use the formula,
.
Here, v is velocity and its value given 26 mi/h ( in m/s,
) and d is distance and its value is given 80 m.
Substituting these values in above formula we get,

Thus, the time delay between green lights on successive blocks to keep the traffic moving continuously is 6.88 s